Titanium alloy for golf-club heads, and clubheads comprising same

ABSTRACT

A driver, fairway wood, utility clubhead or iron having i) a striking face, ii) a striking face insert or iii) a striking face with a metallic cap comprising a titanium alloy consisting essentially of: A) from about 5.5 to about 6.5 percent by weight aluminum; B) from about 1.5 to about 2.2 percent by weight iron; C) from about 0.01 to about 0.1 percent by weight silicon; and D) the balance titanium.

CROSS REFERENCE TO RELATED APPLICATION

This application is a non-provisional application claiming priority to and benefit of U.S. Provisional Patent Application No. 61/142,045, filed Dec. 31, 2008, which is incorporated herein by reference.

FIELD

This disclosure pertains to, inter alia, golf clubs and golf-club heads (“clubheads”). More specifically, the disclosure pertains to the striking face of clubheads of which at least a portion is fabricated of an alloy of titanium (Ti), aluminum (Al), iron (Fe) and Si (Si).

BACKGROUND

A set of golf clubs includes various types of clubs for use in different respective conditions or circumstances in which the ball must be hit during a round of golf. Typically a given set of golf clubs includes a “driver” for hitting the ball (from a tee) the longest distance on a course, several fairway “woods” for hitting the ball (from a tee or not from a tee) shorter distances than the driver, a set of irons for hitting the ball a range of distances that are typically shorter than when hitting the ball using a wood, and at least one putter. The set may also include “utility” or “hybrid” clubs that combine features of a fairway wood and a long iron. Drivers and putters have highly specific respective purposes, whereas with fairway woods, utility clubs, and irons, the golfer's selection of a particular club to use in a particular situation is personal. Shape of the club, ease of use of the club, and personal preference are the usual factors that determine the golfer's choice of club.

A golf club comprises a head (also called a “clubhead”), a shaft affixed to the clubhead, and a grip affixed to the shaft. An exemplary clubhead 10 for a driver is shown in FIGS. 1, where there is shown a golf club head 10 having a metallic body 12 and a striking face insert 14. It will be understood that other clubheads, such as a fairway wood or a utility club, has similar features (but altered in shape and/or configuration as appropriate for the respective type of club).

With respect to drivers and fairway woods, the term “wood” also is based on tradition because such clubs originally were made of wood, but modern clubs of this type are usually made of composite materials and/or metal alloys such that they are now collectively referred to as “metalwoods”. Metal alloys offer certain advantages over wood, such as a higher ratio of strength to weight and greater durability. Alloys conventionally used for this purpose include any of various stainless steels (e.g., 304SS, 255SS, 431SS), Al—Li alloys, Be—Cu alloys, pure titanium (Ti), and certain Ti alloys.

An “alloy” is a mixture of a pure metal with one or more other metals and/or other elements that is formulated to satisfy one or more special purposes that cannot be met by the pure metal. Whenever a metal is alloyed, a respective change usually is imparted to one or more properties of the metal, such as melting temperature, strength, ductility, electrical resistance, thermal conductivity, heat-treatment properties, corrosion resistance, and magnetic properties. The alloy typically is formulated to achieve a particular desired combination of these properties.

In recent years, substantial research and development efforts have been directed at improving golf clubs to enable, inter alia, a larger number of people to have an enjoyable experience playing golf despite having less actual game-playing skill. Exemplary improvements include: (1) increasing the size of the clubheads to increase the size of the “sweet spot” (see below) and thus improving the probability of successful strikes of the ball using the club, (2) lowering the center of gravity of the clubhead to obtain stable striking of the ball, desired loft, and desired trajectory distance, (3) making the clubhead aerodynamic so as to reduce air drag of the clubhead as it is swung, and (4) configuring the sole of the clubhead to reduce friction of the swung clubhead as it moves along the ground just before striking the ball.

Clubhead enlargement has been facilitated by the use of lightweight but strong metals to replace conventional wood and iron. For example, pure titanium (Ti) and Ti alloys have been used increasingly in clubheads. As an example, Ti has a density of about 4.5 g/cm³, compared to steel, which has a density of 7.6-7.9 g/cm³. The relatively high strength of metal has allowed all-metal drivers, woods, and utility clubs to be made hollow, in contrast to the solid construction of many traditional clubs of these types. Recent trends include making the walls of the clubhead as thin as possible to provide maximal discretionary mass. The metals used for making hollow clubheads must have high strength and other mechanical properties that are especially appropriate for golf clubs.

The most widely used Ti alloy in golf clubs is “6-4 Ti,” which contains nominally 6% (w/w) aluminum (Al), nominally 4% (w/w) vanadium (V), and balance Ti. (The 6-4 alloy, according to its specification, also typically includes very small amounts of other elements: maximally 0.08% (w/w) carbon (C), maximally 0.0125% (w/w) hydrogen (H), 0.25% (w/w) iron (Fe), and 0.13% (w/w) oxygen (O).) The “% (w/w)” unit is gravimetric percent, or weight percent. The “6-4” denomination signifies the nominal 6% (w/w) Al and 4% (w/w) V concentrations; hence, this alloy also is termed “6Al-4V Ti.” The actual specification for 6-4 Ti allows up to ±0.5% variations, from nominal, in the Al and V concentrations.

Other alloys conventionally used in golf clubs are “SP700 Ti”, “15-3-3-3 Ti,” and “2041 Ti.” The SP700 alloy contains, nominally, 4.5% (w/w) Al, 3% (w/w) V, 2% (w/w) Fe, 2% (w/w) Mo, balance Ti. The 15-3-3-3 alloy contains, nominally, 15% (w/w) V, 3% (w/w) chromium (Cr), 3% (w/w) Al, 3% (w/w) zirconium (Zr), and balance Ti. The 2041 alloy contains, nominally, 20% (w/w) V, 4% (w/w) Al, 1% (w/w) tin (Sn), and balance Ti.

Ti and Ti alloys provide respective combinations of low density and high strength, and have been used in iron clubheads, in putter heads, and in the heads of drivers and metal fairway woods. As noted above, the low density of Ti and Ti alloys allows the clubhead to be increased in size while maintaining clubhead mass within acceptable limits, compared to a conventional clubhead. The larger clubhead can be configured to provide various benefits, including a larger sweet spot. The high strength of certain Ti alloys allows the walls of the clubhead to be made very thin (e.g., 1 mm or less).

Essentially all metal clubheads are fabricated (or have portions that are fabricated) by one of two widely used manufacturing methods: forging and casting. Forging worked well for earlier, simpler, and more conventional clubhead designs. However, forging oftentimes is incapable of producing complex clubhead geometries and configurations, such as cavity-backs in irons. Additionally, with the recent advent of more highly “engineered” clubheads, including irons, woods, and drivers, it now is desirable that the heads be formed to tighter tolerances than are possible using forging processes to minimize expensive downstream machining steps. As a result, club manufacturers have employed various casting methods, especially investment casting which is used widely in the fabrication of metal woods, drivers, irons, putters, and the like.

Accompanying the current use of more exotic materials in their fabrication, clubheads also typically are “engineered” to provide them with more sophisticated configurations, both internally and externally. For example, as noted above, most types of drivers and woods made at least partially of metal are hollow and have thin walls with interior and exterior configurations that are shaped according to tight specifications. For example, the walls can have any of various ribs, pockets, orifices, and/or other features for enhanced performance. Additionally, certain manufacturers incorporate cartridges, plugs, or the like into or on one or more of the walls to alter the mass distribution of the clubhead and thus provide control over, for example, loft, draw, and/or fade of the shot made using the club. In any event, adding any of these features to a cast clubhead increases the complexity of the cast portion(s) of the clubhead.

In addition the clubhead may have a separate striking face or striking face insert prepared from a metallic cover sheet which is subsequently trimmed so as to conform to a golf club face plate and provide a striking surface for a golf club. The striking face insert may also comprise a composite region and a metallic cap or cover. The striking face, striking face insert or metallic cap or cover may be prepared from a metallic cover sheet which is subsequently trimmed so as to conform to the required shape of the golf club face plate and provide a striking surface for a golf club.

The field of candidate Ti alloys that could be used in golf clubs is very limited because many Ti alloys, while exhibiting high stiffness despite their low mass, are too easily damaged by repeated impacts received during use of the club for striking golf balls. Currently, as noted above, the Ti alloy most widely used for casting clubheads and parts thereof including a separate striking face or striking face insert is Ti-6Al-4V.

Some of the factors that result in the higher cost of titanium-base alloys, such as the cost of the base metal, cannot at present be substantially changed. Factors that are subject to beneficial change from the cost standpoint are the cost of the alloying elements. Specifically, with the conventional Ti-6Al-4V alloy, the vanadium adds significantly to the overall cost of the alloy.

Thus, there is a need for lower cost Ti alloys without the requirement of expensive alloying agents such as vanadium while still having the physical characteristics suitable for use in golf clubs. We have now found that a titanium-based alloy having a good combination of strength and ductility allows the preparation of a clubhead striking face or striking face insert or metallic cap of a striking face insert or a clubhead body with sufficient durability but without the requirement for expensive alloying agents such as vanadium, and thus having a relatively low cost. This low cost alloy composition (“LCAC”) has the following composition;

A) of from about 5.5 to about 6.5., preferably of from about 5.9 to 6.5 percent by weight aluminum;

B) from about 1.5 to about 2.2, preferably of from about 1.4 to about 2.0 percent by weight iron;

C) from about 0.01 and about 0.1, preferably from about 0.01 to about 0.8, most preferably from about 0.01 to about 0.05 percent by weight silicon and

D) the balance titanium.

The alloy may have oxygen restricted to less than 0.2 percent by weight, carbon restricted to less than 0.05 percent by weight, nitrogen restricted to less than 0.04 percent by weight and hydrogen restricted to less than 0.02 percent by weight.

The alloy may be forged at a temperature of 860° to 1160° C., hot-rolled at a temperature of 920° to 980° C., and tempered at a temperature of 840° C.

The resulting low-cost alloy may be produced in the form of hot rolled or cold rolled sheets, and have the mechanical properties which include i) a yield strength of from about 400 to about 1500, preferably from about 600 to about 1200, more preferably from about 800 to about 1000 MPa; ii) a tensile strength of from about 400 to about 1500, preferably from about 600 to about 1400, more preferably from about 800 to about 1200 MPa, a ductility of >10%, a Rockwell hardness of from about 25 to 55, preferably from about 27 to about 50 and most preferably from about 30 to about 40 HRC, and a modulus of from about 115 to about 135, preferably from about 120 to about 130 GPa. When used as a separate striking face or striking face insert and subjected to endurance testing during which the parts were subjected to repeated impacts at a ball speed of about 40-50 m/s, not only were the striking face inserts able to demonstrate an endurance of >7000 shots with a deflection <0.1 mm, but the average characteristic ball contact time (CT) with the strike plate measured during the endurance test was also similar to those of much higher cost alloys such as the conventional Ti-6Al-4V alloy.

SUMMARY

In one aspect the present invention relates to a golf club head, having a club body; and a striking face which includes a titanium alloy consisting essentially of about 5.5 to about 6.5 percent by weight aluminum; about 1.5 to about 2.2 percent by weight iron; about 0.01 and about 0.1 percent by weight silicon and the balance titanium.

In another aspect the present invention relates to a golf club head, having a club body; and a striking face insert which includes a titanium alloy consisting essentially of about 5.5 to about 6.5 percent by weight aluminum; about 1.5 to about 2.2 percent by weight iron; about 0.01 and about 0.1 percent by weight silicon and the balance titanium.

In another aspect the present invention relates to a golf club head, having a club body; and a striking face insert which includes a metallic cap which includes a titanium alloy consisting essentially of about 5.5 to about 6.5 percent by weight aluminum; about 1.5 to about 2.2 percent by weight iron; about 0.01 to about 0.1 percent by weight silicon and the balance titanium.

In another aspect the present invention relates to a golf club head, having a club body; which includes a titanium alloy consisting essentially of about 5.5 to about 6.5 percent by weight aluminum; about 1.5 to about 2.2 percent by weight iron; about 0.01 to about 0.1 percent by weight silicon and the balance titanium.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the illustrative drawings, and particularly FIG. 1, there is shown a golf club head 10 having a metallic body 12 and a face insert 14, the face insert 14 is durable and yet lightweight. In a preferred embodiment, the body 12 is formed by investment casting a titanium alloy. With the face insert 14 in place, the club head 10 preferably defines a volume of at least 200 cc and more preferably a volume of at least 300 cc. FIG. 2 shows a face insert comprising a composite region 16 and a metallic cap 18.

DETAILED DESCRIPTION

This disclosure is set forth in the context of representative embodiments that are not intended to be limiting in any way.

Concentration is expressed herein as “percent by weight or % (w/w),” which is a gravimetric percent. For example, with respect to an alloying element, a concentration of 4% (w/w) is 4% based on the weight of the alloying element relative to a unit mass of the alloy.

The Titanium Alloys

The metallurgy of titanium is dominated by an allotropic crystallographic transformation that occurs in the pure metal at a “transus” temperature of about 882° C. (The transus temperature is far below the melting temperature of pure titanium, which is about 1670° C.) Below the transus temperature, pure Ti has a hexagonal close-packed (“HCP”) structure called “alpha-phase” (α-phase). Above the transus temperature, pure Ti has a body-centered cubic (“BCC”) structure called “beta-phase” (β-phase). Thus, at room temperature, pure titanium has α-phase structure, which is stable up to the transus temperature. The β-phase structure is stable from the transus temperature to the melting temperature.

One fundamental effect of adding alloying elements to Ti is an alteration of the transus temperature, which can provide control of the α- and β-phases. Titanium alloys are categorized as being “α-alloys,” “β-alloys,” or “α+β-alloys.”

Elements having high solubility in the α-phase but not in the β-phase tend to raise the transus temperature and hence are called “α-stabilizers.” A key α-stabilizer is aluminum (Al), which is very effective at lower concentrations. (Also, Al is advantageously light in mass.) But, the amount of Al that can be added to Ti is limited because, at higher concentrations (generally >8% (w/w)), Al tends to form a brittle Ti aluminide (predominantly Ti₃Al) compound. Other α-stabilizers are the so-called “interstitial” elements oxygen (O), nitrogen (N), and carbon (C).

Elements that lower the transus temperature, that readily dissolve in and strengthen the β-phase, and that have low solubility in the α-phase are called “β-stabilizers.” Typical β-stabilizers are chromium (Cr), niobium (Nb), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), tantalum (Ta), and vanadium (V). Mo and V are the most important of the α-stabilizers and are termed “β-isomorphous” elements due to their complete mutual solubility in β-phase Ti.

A Ti alloy containing substantially only one or more α-stabilizers (such as Al) is called an “α-alloy” or a “near-α-alloy.” The α-alloys and near-α-alloys generally have good strength. A small amount of β-stabilizer enhances formability of these alloys.

The addition to Ti of certain controlled amounts of one or more β-stabilizers causes at least some β-phase to exist, along with α-phase, in the alloy below the transus temperature. The resulting alloy at room temperature is a two-phase alloy (called an “α+β-alloy”). Of the various Ti alloys that are available, the best-known and most common α+β-alloy (including for fabricating the heads of golf clubs) is the Ti-6Al-4V alloy (also called “6-4 Ti” alloy; containing nominally 6% (w/w) Al and nominally 4% (w/w) V, wherein Al stabilizes and strengthens the α-phase while V provides a significant amount of β-phase). The SP700 Ti alloy also is an α+β-alloy due to its nominal Al concentration of 4.5% (w/w) and nominal V and Mo concentrations of 3% (w/w) and 2% (w/w), respectively. The α+β-alloys generally have good to high strength.

Ti alloys containing at least one β-stabilizer and little to no α-stabilizers are called β-alloys.” (Mo and V tend to have the greatest influence on β-stability.) The 15-3-3-3 Ti alloy and the 2041 Ti alloy are β-alloys due to their nominal concentrations of 15% (w/w) V and 20% (w/w) V, respectively. The β-alloys generally have lower resistance to deformation (greater ductility) than the α-alloys, which facilitates their rollability and formability (e.g., in cold-rolled-sheet form) for fabricating strike plates for golf clubs.

U.S. Pat. Nos. 5,219,521 and 5,342,458 (the entire contents of both of which are herein incorporated by reference) has disclosed and alpha-beta titanium-based alloy with no vanadium and a method for its processing. We have now discovered that use of such a titanium-based alloy allows the preparation of a clubhead striking face or striking face insert or metallic cap of a striking face insert or a clubhead body each with sufficient mechanical properties and without the requirement for expensive alloying agents such as vanadium and thus having a relatively low cost composition. This low cost alloy composition (“LCAC”) consists essentially of;

A) from about 5.5 to about 6.5., preferably of from about 5.9 to 6.5 percent by weight aluminum;

B) from about 1.5 to about 2.2, preferably of from about 1.4 to about 2.0 percent by weight iron;

C) from about 0.01 to about 0.1, preferably from about 0.01 to about 0.8, most preferably from about 0.01 to about 0.05 percent by weight silicon and

D) the balance titanium.

By “consist essentially of is meant that, whereas the subject LCAC contains the elements listed above (in the respective concentrations listed above), the alloys also can contain incidental elements at small (“impurity”-level) amounts that are much less than 0.5%. These incidental elements can include, but are not necessarily limited to, oxygen restricted to less than 0.2 percent by weight, carbon restricted to less than 0.05 percent by weight, nitrogen restricted to less than 0.04 percent by weight and hydrogen restricted to less than 0.02 percent by weight.

The LCAC may be produced in the form of hot rolled or cold rolled sheets, and have the mechanical properties which include i) a yield strength of from about 400 to about 1500, preferably from about 600 to about 1200, more preferably from about 800 to about 1000 MPa; ii) a tensile strength of from about 400 to about 1500, preferably from about 600 to about 1400, more preferably from about 800 to about 1200 MPa, a ductility of >10%, a Rockwell hardness of from about 25 to 55, preferably from about 27 to about 50 and most preferably from about 30 to about 40 HRC, and a modulus of from about 115 to about 135, preferably from about 120 to about 130 GPa.

With reference to the illustrative drawings, and particularly FIG. 1, there is shown a golf club head 10 having a body 12 and a face insert 14, the face insert 14 is durable and yet lightweight. In one aspect of the present invention, the body 12 is formed by investment casting a titanium alloy and the face insert 14 comprises the LCAC alloy and may be attached to the metallic body 12 e.g., by welding or brazing.

It will be understood that other clubheads, such as a fairway wood or a utility club, has similar features (but altered in shape and/or configuration as appropriate for the respective type of club). With the face insert 14 in place, the club head 10 preferably defines a volume of at least 200 cc and more preferably a volume of at least 300 cc. The club head 10 has superior durability and club performance, including preferably a coefficient of restitution (COR) of at least 0.79.

The clubhead body 12 can be integrally formed using techniques such as molding, cold forming, casting, and/or forging and the face insert 14 can be attached to the body by means known in the art. For example, the striking face 14 can be attached to the body 10 as described in U.S. Patent Application Publication Nos. 2005/0239575 and 2004/0235584. The body 10 can be made from a metal alloy (e.g., titanium, steel, aluminum, and/or magnesium), composite material, ceramic material, or any combination thereof The body 10 can also have a thin-walled construction, such as described in U.S. application Ser. No. 11/067,475, filed Feb. 25, 2005, which is incorporated herein by reference.

In addition to the face insert 14 being made from the LCAC, it may also have a variable thickness such as described in U.S. Pat. Nos. 6,997,820, and 6,904,663, the contents of each of which are incorporated herein by reference.

When used as a separate striking face or striking face insert and subjected to endurance testing during which the parts were subjected to repeated impacts at a ball speed of about 40-50 m/s, not only were the striking face inserts able to demonstrate an endurance of >7000 shots with a deflection <0.1 mm, but the average characteristic ball contact time (CT) with the strike plate measured during the endurance test was also similar to those of much higher cost alloys such as the conventional Ti-6Al-4V alloy, while providing a greater than 20% savings in material cost.

The subject LCAC striking face insert is weldable, and can be welded to the body made of other titanium alloys. For example, the subject to LCAC face insert can be welded to a body component cast of any of various β-alloys of Ti typically used for fabricating clubhead bodies. Since Ti alloys oxidize when heated in air, welding must be performed in a rarified or inert environment. Vacuum welding can be performed using an electron beam or laser beam in a vacuum chamber or by the conventional “tungsten inert gas” (TIG) method. Further desirably, TIG welding can be performed using welding rods made of the same alloy as the parts being welded so as to avoid or at least minimize depleting the weld of aluminum, for example. Controlling the alloy concentration of welds produces stronger and more shadow-free welds.

An alternative method of assembling the cast body and LCAC striking face insert is adhesive bonding, which requires the use of an adhesive. The choice of a specific adhesive will depend upon the particular material to which the LCAC component is being bonded and the particular stresses to which the cured adhesive joint must be resistant. Exemplary adhesives include, but are not limited to, two-part epoxy adhesives such as DP420 and DP460 manufactured by 3M (Minneapolis, Minn.), acrylic adhesives such as DP810 manufactured by 3M, any of various urethane adhesives, and film adhesives such as AF-42 manufactured by 3M.

Another alternative method of assembling the LCAC striking face insert to another component is mechanical joining by pressing to form, for example, a press fit or lip encasement as commonly practiced by persons of ordinary skill in the art of clubhead manufacturing. In this regard, reference is made for example to U.S. Pat. No. 5,697,855 and U.S. Pat. No. 6,743,114, which discuss these techniques.

Yet another alternative method of assembling the LCAC striking face insert to another component is mechanical joining by use of mechanical fasteners such as rivets, screws, or analogous fasteners as commonly practiced by persons of ordinary skill in the art of clubhead manufacturing.

In another aspect of the present invention and as shown in FIG. 2, the striking face insert may comprise a lightweight region 16 and a metallic cap 18 comprising the LCAC. Materials suitable for the lightweight region 16 include the composite materials described in U.S. Pat. No. 7,267,620 and pending U.S. patent application Ser. Nos. 11/825,138 (filed on Jul. 2, 2007), 11/960,609, 12/004,386 and 12/004,387 (all filed on Dec. 19, 2007), 12/332,210 (filed on Dec. 10, 2008) and 12/156,947 (filed on Jun. 3, 2008) the contents of each of which are incorporated herein by reference. Alternatively, the lightweight region 16 may comprise any non-metallic material having a density less than a metallic material of the body 12 along with a metallic cap 18 comprising the LCAC covering a front surface of the face insert 14 and having a rim 36. For example, the face insert 14 of the present invention in addition to comprising a composite material, such as a fiber-reinforced plastic or a chopped-fiber compound (e.g., bulk molded compound or sheet molded compound), may also comprise an injection-molded polymer either alone or in combination with prepreg plies of the composite. The thickness of the face insert 14 may be substantially constant or it may comprise a variation of at least two thicknesses, one being measured at a geometric center and another measured near a periphery of the face insert 14. The total thickness of the face insert 14 may range between about 1 mm and about 8 mm, preferably between about 2 mm and about 7 mm, more preferably between about 2.5 mm and about 4 mm, and most preferably between about 3 mm and about 4 mm.

In one aspect of the present invention and with reference to FIG. 4, the striking face insert 14 comprising a composite lightweight region 16 and a metallic cap comprising the LCAC, 18 has sufficient structural strength that excessive reinforcement along the interface of the body 12 and the face insert 14 is not required, which further enhances beneficial weight allocation effects. In this embodiment, the body 12 is formed of a titanium alloy, Ti-6Al-4V; however, other suitable material can be used. The face insert 14 is supported by an annular ledge 32 and is secured preferably with an adhesive. The annular ledge 32 preferably has a thickness of about 1.5 mm and extends inwardly between about 3 mm to about 6 mm. The annular ledge 32 is sufficiently recessed to allow the face insert 14 to sit generally flush with a transition edge 34 of the body. Although, in this embodiment, the annular ledge 32 extends around the periphery of the front opening, it will be appreciated that other embodiments can utilize a plurality of spaced annular ledges, e.g., a plurality of tabs, to support the face insert 14.

With continued reference to FIG. 4, the metallic cap 18 of the face insert 14 includes a rim 36 about the periphery of the composite region 16. In a preferred embodiment, the metallic cap 18 may be attached to a front surface of the face insert 14, wherein the combined thickness of the composite region 16 and the metallic cap 18 of the face insert 14 are no greater than the depth D of the annular ledge 32 at the front opening of the body 12. The rim 36 covers a side edge 38 of the composite region 16 to further protect against peeling and delamination of the composite. Preferably, the rim 36 has a height substantially the same as the thickness of the face insert 14. In an alternative embodiment, the rim 36 may comprise a series of segments instead of a continuous cover over the side edge 38 of the composite region 16. The metallic cap 18 and rim 36 may be formed, for example, by stamping or other methods known to those skilled in the art. A preferred thickness of the metallic cap 18 is less than about 0.5 mm, and more preferably, it is less than about 0.3 mm.

Preferably, the thickness of the composite region 16 is about 4.5 mm or less and the thickness of the metallic cap 18 is about 0.5 mm or less. More preferably the thickness of the composite region 16 is about 3.5 mm or less and the thickness of the metallic cap 18 is about 0.3 mm or less. The metallic cap comprises the LCAC.

The metallic cap 18 defines a striking face 40 having a plurality of grooves 42. The metallic cap 18 further aids in resisting wear from repeated impacts with golf balls even when covered with sand. Preferably, a bond gap 44 of about 0.05 mm to 0.2 mm, and more preferably about 0.1 mm, is provided for adhesive attachment of the metallic cap 18 to the composite region 16. In an alternative embodiment, the bond gap 44 may be no greater than 0.2 mm. The clubhead body or portion thereof, can include one or more weighting elements formed from one or more high-density materials (e.g., tungsten, lead, etc.) strategically placed so as to place the CG of the clubhead at the desired locus. The clubhead or portion thereof also or alternatively can include one or more inserts or applied bodies as used for vibration control or damping, acoustic control or damping, COR manipulation, or the like.

In another aspect of the invention the clubhead may comprise a striking face and a return portion comprising the LCAC, the striking face and return portion extending laterally inward from the perimeter of the striking plate portion which generally includes an upper lateral section, a lower lateral section, a heel lateral section and a toe lateral section to engage the aft portion of the clubhead body. Thus, the return preferably encircles the striking plate portion a full 360 degrees. However, those skilled in the pertinent art will recognize that the return portion may only encompass a partial section of the striking plate portion, such as 270 degrees or 180 degrees, and may also be discontinuous. A description of such a clubhead striking face and return portion is more fully described in U.S. Pat. No. 7,128,661, the description in which is herein incorporated by reference. The aft portion of the clubhead body which engages, or is engaged by, the return portion may comprise be a titanium alloy, including but not limited to the LCAC but also may comprise a non-metal material, preferably a composite material such as continuous fiber pre-preg material (including thermosetting materials or a thermoplastic materials for the resin). Other materials for the aft-body include other thermosetting materials or other thermoplastic materials such as injectable plastics. The aft-body is preferably manufactured through bladder-molding, resin transfer molding, resin infusion, injection molding, compression molding, or a similar process. In a preferred process, the face component, with an adhesive on the interior surface of the return portion, is placed within a mold with a preform of the aft-body for bladder molding. A bladder is placed within the hollow interior of the preform and face component, and is pressurized within the mold, which is also subject to heating. The co-molding process secures the aft-body to the face component. Alternatively, the aft-body is bonded to the face component using an adhesive, or mechanically secured to the return portion.

In another aspect of the present invention the clubhead in addition to having any of the aforementioned striking face configurations may also include a clubhead body cast from a titanium alloy including but not limited to the LCAC. Casting of the clubhead body 10 can be performed by any of various methods, such as but not necessarily limited to, investment casting, levitation casting, centrifugal casting, and sand casting.

At high temperatures, titanium is very reactive, especially with oxygen and nitrogen from the atmosphere, and with hydrogen. Consequently, melting of titanium is usually performed in a rarified (“vacuum”) environment, and casting of titanium alloys is performed under a rarified or inert (e.g., argon) atmosphere to avoid undesired changes to the alloy.

Sand casting is performed in a conventional manner used for casting other metals, except for having to cast in an inert atmosphere. Sand casting is seldom used for casting golf-club parts because of the inability of this technique to form the currently desired fine details and tight tolerances. Also, parts formed by sand casting usually require a large amount of finish machining.

Investment casting can provide tight tolerances and fine configurational detail currently desired for forming clubheads, and thus can minimize downstream machining and finishing steps. Any of the various investment casting processes commonly used in golf club manufacture can be used. Levitation casting can be performed as described in U.S. Pat. No. 5,193,607 to Demukai et al., U.S. Pat. No. 5,042,561 to Chandley (both incorporated herein by reference) or by other suitable method. Whereas molten metal traditionally is poured from a crucible down to a mold, in levitation casting the molten metal is suspended in space, melted, and urged into a mold (usually made of a ceramic material) by suction. Melting is usually performed in a water-cooled copper crucible. The process yields a substantially contaminant-free melt of titanium, cleaner castings, and good yield of the cast product. Heat loss from the melt is kept low by reducing the area in which molten metal contacts the crucible.

The casting process can also be tailored such that any component of the clubhead body can include one or more cartridges, weighting elements, and/or inserts or applied bodies as used for CG placement, vibration control or damping, acoustic control or damping, COR (coefficient of restitution) manipulation, or the like.

Before and/or after joining together the body component to another component, any necessary finish machining (cutting, milling, drilling, boring, grinding, smoothing, polishing) and surface treatment (plating, painting, coating) steps are performed as required or desired. The various finish-machining steps are well known to persons of ordinary skill in the relevant art and are not described herein.

After completing any required finish-machining steps, it may be desirable to execute a suitable surface treatment of the clubhead, such as by plating, painting, powder coating, carburizing, passivating, or other process. These various processes are familiar to persons of ordinary skill in the relevant art. 

1. A golf club head, comprising: a club body; and a striking face wherein the striking face comprises a titanium alloy consisting essentially of; A) from about 5.5 to about 6.5 percent by weight aluminum; B) from about 1.5 to about 2.2 percent by weight iron; C) from about 0.01 to about 0.1 percent by weight silicon; and D) the balance titanium.
 2. A golf club head, comprising: a club body; and a striking face insert wherein the striking face insert comprises a titanium alloy consisting essentially of; A) from about 5.5 to about 6.5 percent by weight aluminum; B) from about 1.5 to about 2.2 percent by weight iron; C) from about 0.01 to about 0.1 percent by weight silicon; and D) the balance titanium.
 3. A golf club head, comprising: a club body; and a striking face insert wherein the striking face insert comprises a metallic cap comprising a titanium alloy consisting essentially of A) from about 5.5 to about 6.5 percent by weight aluminum; B) from about 1.5 to about 2.2 percent by weight iron; C) from about 0.01 to about 0.1 percent by weight silicon; and D) the balance titanium.
 4. A golf club head comprising: a club body; and a striking face component composed of a titanium alloy material, the face component comprising a striking plate portion and a return portion; and wherein the titanium alloy consists essentially of; A) from about 5.5 to about 6.5 percent by weight aluminum; B) from about 1.5 to about 2.2 percent by weight iron; C) from about 0.01 to about 0.1 percent by weight silicon; and D) the balance titanium.
 5. The golf clubhead of claim 4 wherein the club body comprises a composite material.
 6. The golf clubhead of claim 1, 2, 3 or 4 wherein the club body comprises a titanium alloy.
 7. The golf club head of claim 6 wherein the titanium alloy consists essentially of; A) from about 5.5 to about 6.5 percent by weight aluminum; B) from about 1.5 to about 2.2 percent by weight iron; C) from about 0.01 to about 0.1 percent by weight silicon; and D) the balance titanium.
 8. The clubhead of claim 1, 2, 3 or 4 wherein the golf club is configured as a driver, fairway wood, utility clubhead or iron. 